This invention relates to a method for opening an envelope, in which the envelope is displaced in a direction of transport along a circular cutting edge rotatable in a plane parallel to the direction of transport and the cutting edge makes at least one incision in at least one wall of the envelope.
Such a method is known from Swiss patent specification 648 794. In this known method, the envelopes are heated by means of a spiral filament in the area where the incision is to be made, in order to remove or weaken a coating, if any, on the paper to be cut, so that the incision can be made with greater reliability. This solutions however, complicates the construction of the envelope opener considerably because special materials are necessary to obtain the required heat resistance in the area of the spiral filament and to avoid the envelope opener reaching so high a temperature in a large area around the spiral filament as to give rise to the risk of burns. A further disadvantage of this solution is that in the case where an envelope gets stuck at the location of the spiral filament, there is a danger of the contents getting singed or burnt. Due to the possibility of the envelope catching fire, the apparatus moreover constitutes a substantial fire hazard.